The present invention relates to a method of producing a semiconductor device, an apparatus for use in the method, and an article produced by the method. More specifically, the present invention relates to a novel method of and a novel apparatus for relieving a defective circuit in a circuit such as an LSI (i.e., Large Scale Integrated) circuitin the producing process of a semiconductor device by making use of a redundant circuit.
In a semiconductor device, especially, in a semiconductor memory device composed of a number of circuits having an identical structure, in order to prevent the device as a whole from becoming defective by the defect of a portion of the circuits thereby to improve the production yield of the device, there has been adopted a method by which the so-called "redundant circuit" is formed integrally with the device so that the defective circuit may be replaced by that redundant circuit. In the semiconductor device having the redundant circuit structure, rows and columns containing the defective bits are replaced by the spare rows and columns by making use of the programming technique.
A fuse is used for that circuit replacement and is made of polycrystalline silicon (i.e., polysilicon) or the like to form a part of the redundant circuit so that it may be electrically cut to effect the defect relief (or the circuit replacement). Incidentally, an RAM (i.e., Random Access Memory) of large capacitance having the redundant structure is disclosed in NIKKEI ELECTRONICS, 1981. 12. 7, pp. 219 to 226, which was published in December, by Nikkei-MacGraw-Hill, Inc.
Here, the following two methods are conceivablee as that defect relieving method. As shown in FIGS. 4(A) to 4(C), specifically, a fuse 1 is formed of a polysilicon or metal silicide film on the surface insulating film 3 of a semiconductor substrate or a silicon substrate 2 and is overlaid by interlayer insulating films (such as a SiO.sub.2 film 4, a first PSG film 5 and a second PSG film 6), an aluminum wiring film 7 and by a protection film 8 such as a plasma silicon nitride film. And, the fuse 1 is fused by exposure to a laser beam. Since the aforementioned protection film 8 shields the beam, however, it is formed in advance with an opening (or aperture) 9, as shown in FIG. 4(A), so that the fuse 1 may be exposed through that opening 9 to a laser beam 10, as shown in FIG. 4(B), and may be fused to replace the circuit. In addition, as shown in FIG. 4(C), another protection film 11 is formed again to protect the aforementioned opening. According to the second method shown in FIGS. 5(A) to 5(C), on the other hand, characteristic inspections are conducted to fuse the fuse 1 before the protection film is formed, as shown in FIGS. 5(A) and 5(B), and then the protection film 11 is first formed, as shown in FIG. 5(C), to protect the respective portions.
Despite this fact, the former method described with reference to FIGS. 4(A) to 4(C) is required to have the two steps of forming the protection films so that the number of steps is increased to raise a problem that the production cost is increased. On the other hand, the latter method described with reference to FIGS. 5(A) to 5(C) has to conduct the characteristic inspections and the relief in the absence of the protection film 11, although the step number is not increased, with a resultant fear that the product may be contaminated by the intervening handling or the like to raise a problem that the production yield and/or reliability is degraded.